Rentricity Uses Pressure in City Pipes to Make Electricity

Most of the drinking water in Keene, N.H., flows from two reservoirs at an elevation several hundred feet above the city’s water treatment plant. It arrives there at a high pressure that needs to be reduced nearly tenfold for treatment. In February, Keene began using that excess water pressure to spin two turbines plugged into the pipe by a New York City startup called Rentricity, using small generators to make electricity from water pressure that was previously dissipated by a mechanical valve. “What we’re really trying to do is recover energy that’s just not being tapped into and use it to make [utilities] more efficient,” says Rentricity founder Frank Zammataro.

The 53-year-old former Merrill Lynch technology executive is one of dozens of entrepreneurs trying to capture so-called hydrokinetic power from moving water in rivers, oceans, or, in Rentricity’s case, pipes. Such projects are distinct from traditional hydroelectric power because they tap into existing flows, rather than dam rivers. Joe Sweet, a researcher at the Connecticut Center for Entrepreneurship and Innovation who co-authored a report on hydrokinetics last year, says the industry is young and “it hasn’t been really settled what’s going to be the best commercially applied technology.” Zammataro says the economics of Rentricity’s projects are more appealing than other types of clean energy because they can count on consistent and predictable water flows, unlike solar or wind generators that depend on the weather. The equipment has a 40-year life span, and energy savings will cover the cost in three to 16 years, depending on the size of the installation and the clean energy incentives in place, he adds.